Research And Screening Of Pretreatment Methods For Pesticides And Their Degradation Products In Water Environment

Pesticide chemical pollution is one of the important factors affecting water quality.Currently,there are more than 1,400 registered pesticides in the world,of which about 500 are commonly used.When pesticides enter the environment,they will not only exist in the form of the parent compound,but also produce degradation products.In addition,the complexity of environmental media makes the requirements for detection methods increasingly higher.Therefore,the establishment of an efficient,fast and sensitive sample preparation method to achieve the enrichment,extraction and purification of pesticides and their degradation products is the key to the correct assessment of pesticide pollution in the water environment.In the sample pretreatment technology of pesticide and their degradation products,the traditional methods such as soxhlet extraction,oscillating extraction and liquid-liquid extraction are tedious and error-large,as well as the consumption of a large number of organic solvents is easy to cause environmental pollution.With the development of science and technology,new sample analysis pretreatment techniques are emerging,such as solid phase extraction and accelerated solvent extraction.These new sample pretreatment techniques are improved on the principles of traditional techniques,and the pretreatment process is more systematic and standardized by means of automation,thereby ensuring the accuracy and stability of sample analysis.Taking pesticides and their degradation products as the research object,this paper established a sample pretreatment method for the analysis of pesticides and their degradation products in water and sediment,and discussed their application in actual environmental samples.In this work,a sequential-mode solid phase extraction cartridge was successfully prepared as a sample pretreatment device combined with high performance liquid chromatography-high resolution mass spectrometry to quantitatively analyze pesticides and their degradation products in water.Sequential-mode solid phase extraction cartridge consists of hydrophilic-lipophilic balanced polymer HLB sorbents,strong anion exchange SAX sorbents and strong cation exchange SCX sorbents.HLB sorbents has reversed-phase retention.Both SAX sorbents and SCX sorbents have the properties of non-polar adsorption and ion exchange.By combining the different retention mechanisms of the three adsorbents,the pesticides and their degradation products in water can be extracted and purified at the same time,making the test results more accurate.Under the optimal experimental conditions,the recovery of pesticides and their degradation products is 76%-97%,the relative standard deviation is less than 10%,and the detection limit of the method is 0.0010-41 ng·L-1.The experimental results show that the method is sensitive and reproducible,and is suitable for the detection of pesticide residues in environmental water samples.An accelerated solvent extraction method combined with solid phase extraction purification method was used to establish a pretreatment analysis method for pesticides and their degradation products in environmental sediment,which improved the application scope of the pretreatment method.The factors affecting the extraction efficiency,such as extraction solvent,extraction time,purification column type and eluent volume,were optimized.The effects of moisture content and humic acid of sediment were investigated.Under optimized conditions,the recovery rate of the method is 80%-106%,and the detection limit of the method is 0.0020-0.37μg·kg^-1.This method has the advantages of fast,sensitive and simple operation,and can be applied to the analysis and determination of pesticides in environmental sediment samples.High-throughput qualitative and quantitative screening of pesticides and their degradation products in surface water during the wet and dry season in Shandong was studied using the sequential-mode solid phase extraction cartridge.During the monitoring period,65pesticides and their degradation products were detected in the mixed water,Yellow River water and mountain water.The 10 typical pesticide pollutants with high detection rates were:atrazine,prometryn,simetone,atraton,diethyltoluamide,carbendazim,tebuconazole,tricyclazole,paclobutrazol and atrazine-desethyl,the concentration of which ranged from several to several hundred ng·L^-1.The pesticide pollution in this area was significantly affected by season,and the total pesticide concentration decreased from the dry season to the wet season.Under the influence of agricultural non-point source pollution and other factors,pesticide residues and pollution in three different water bodies were different.